Marijuana Use in the U.S. Has Increased, But Not Because of Legislation, Study Says

American adults are smoking more pot, but increased cannabis use does not appear to be due to wider availability of legal marijuana, a new study from the Public Health Institute's Alcohol Research Group shows.

"Results ...did not show significant increases in use related to medicinal marijuana legislation,” lead investigator William Kerr said in a statement. “It appears that the passage of these policies reflects changing attitudes toward marijuana use, rather than the other way around.”

Overall, 12.9 percent of adults used marijuana in 2015, up from 6.7 percent 10 years earlier, the study revealed. However, it did not find a significant intersection between higher rates of pot use and legislation, which has legalized medical marijuana in 29 states and permitted recreational smoking in eight states—Washington, Oregon, Colorado, California, Nevada, Alaska, Massachusetts and Maine—plus the District of Columbia.